JP2011232487A - Electrophotographic photoreceptor and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor of which charge generating substance has no less high sensitivity than a Y type titanyl phthalocyanine pigment and also no humidity dependency of sensitivity, and an image forming apparatus using the electrophotographic photoreceptor.SOLUTION: An electrophotographic photoreceptor comprises a photosensitive layer which includes a pigment containing at least either a titanyl phthalocyanine and (2R,3R)-2,3-butanediol adduct or the titanyl phthalocyanine and (2S,3S)-2,3-butanediol adduct, and the pigment of which D50 particle size is 100-300 nm and D10 particle size is 50-200 nm.

Description

  The present invention relates to an electrophotographic photosensitive member having high sensitivity and no humidity dependency, and an image forming apparatus using the same.

  In recent years, with the development of electronic equipment, the frequency of use of copying machines and printers using electrophotography has increased, and high-sensitivity electrophotographic photoreceptors (hereinafter sometimes simply referred to as photoreceptors) have been announced one after another. ing. In particular, Y-type titanyl phthalocyanine (hereinafter simply referred to as Y-type pigment) having a maximum peak at 27.2 ± 0.2 ° with a Bragg angle 2θ in the powder X-ray diffraction spectrum is known as a highly sensitive material, and is reported in an academic conference. It has also been. Furthermore, it has been found that the photon efficiency is reduced by dehydration treatment of this Y-type titanyl phthalocyanine in a dry inert gas. Since the quantum efficiency increases again when water is reabsorbed by leaving it in a room temperature and humidity environment, the Y-type pigment has a crystal structure containing water, and the exciton holes and electrons generated by the water molecules by light It is speculated that this is one of the causes of high photon efficiency.

  In an organic photoreceptor using such a material as a charge generation material, there has been a concern that sensitivity characteristics may change due to environmental changes, particularly humidity fluctuations. The disadvantage that the Y-type pigment has a large humidity dependency of sensitivity has recently become increasingly problematic as high image quality is required. For example, if it rains at night and clears the next day, the sealed part of the organic photoconductor (near the developing unit) maintains the high humidity atmosphere of the previous day, and it is between the other open parts of the photoconductor. A difference in sensitivity occurs, and a belt-like image defect occurs due to the difference in sensitivity in an intermediate density image immediately after the start of operation in the morning.

  In order to solve this humidity dependency, there has been an attempt to impart another polar group to the Y-type pigment instead of water, and an adduct titanyl phthalocyanine pigment with 2,3-butanediol has also been reported (Patent Literature). 1).

  Furthermore, a titanyl phthalocyanine adduct of 2,3-butanediol having stereoregularity has been reported as having particularly excellent properties (Patent Documents 2 and 3). A titanyl phthalocyanine adduct of diol and a mixed crystal of titanyl phthalocyanine have been reported as highly sensitive pigments (Patent Document 4).

  However, all of these published technologies have improved humidity dependency of sensitivity. However, the sensitivity is insufficient compared to the Y-type pigment, and long-term exposure under severe conditions such as high temperature and high humidity. When using the photosensitive member, there is a problem that the image density cannot be sufficiently obtained due to the fluctuation of the potential, and further image fogging occurs.

  For this reason, in order to adopt it for organic photoconductors such as high-speed digital copiers that require high image quality, high speed, and high durability, along with improved humidity dependence, higher sensitivity and repeated potential stability It is necessary to ensure.

JP-A-5-273775 JP 7-173405 A Japanese Patent Laid-Open No. 8-82942 Japanese Patent Laid-Open No. 9-230615

  The present invention has been made to solve the above problems.

  That is, an object of the present invention is to provide an electrophotographic photosensitive member in which the charge generating material has a high sensitivity comparable to that of Y-type titanyl phthalocyanine, has a high repetitive potential stability, and has no humidity dependency on sensitivity, and an image using the same. It is to provide a forming apparatus.

  The object of the present invention is achieved by having the following configuration.

  1. In an organic photoreceptor having a photosensitive layer on a conductive support, the photosensitive layer comprises titanyl phthalocyanine and (2R, 3R) -2,3-butanediol adduct or titanyl phthalocyanine and (2S, 3S) -2,3- An electrophotographic photoreceptor comprising a pigment containing at least one of butanediol adducts, wherein the pigment has a D50 particle size of 100 to 300 nm and a D10 particle size of 50 to 200 nm.

  However, the D50 particle size and the D10 particle size follow the measurement methods and definitions described below.

  Measuring method: 500 pigment particles taken with a scanning electron microscope (SEM) photograph are randomly taken out (overlapping particles are the uppermost particles), and the major axis of each particle is measured.

  Definition of D50: D50 is the particle diameter when the particles are accumulated from the smallest particles and the accumulated amount reaches 50% (250 particles) of the total number of particles.

  Definition of D10: D10 is a particle diameter when the particles are accumulated from the smallest particles and the accumulated amount reaches 10% (50 particles) of the total number of particles.

  2. 2. The electrophotographic photosensitive member according to 1 above, wherein the pigment has a circularity of 0.8 to 0.9.

  3. Means for forming an electrostatic latent image on the electrophotographic photosensitive member according to 1 or 2, means for developing the electrostatic latent image with toner, means for transferring the formed toner image to an image support, post-transfer An image forming apparatus comprising at least means for fixing a toner image.

  According to the present invention, there is provided an electrophotographic photosensitive member in which the charge generation material has a high sensitivity comparable to that of Y-type titanyl phthalocyanine, high repetitive potential stability, and no sensitivity humidity dependency, and an image forming apparatus using the same. I can do it.

An X-ray diffraction spectrum of 2,3-butanediol adduct titanyl phthalocyanine has a characteristic peak at a Bragg angle 2θ (± 0.2 °) of 9.5 ° (9.5 ° type), 8.3 The spectrum diagram of phthalocyanine having a characteristic peak at ° (8.3 ° type). 1 is a cross-sectional configuration diagram of a color image forming apparatus using an electrophotographic photosensitive member of the present invention. A spectrum diagram of Y-type titanyl phthalocyanine having a characteristic peak at a Bragg angle 2θ (± 0.2 °) of 27.2 ° in an X-ray diffraction spectrum.

  The configuration of the present invention, the materials used, and the configuration of the image forming apparatus used in the present invention will be described below.

  Generally, the photosensitive layer is formed by coating and drying a coating solution in which a charge generating material is dispersed in a solution in which a binder resin is dissolved in an organic solvent. In order to enhance the electrical characteristics and image characteristics of the photoreceptor, it is considered important to uniformly disperse the charge generating material in the photosensitive layer. When the dispersion is insufficient, coarse particles are contained in the coating solution, and as a result, the photosensitive layer formed using the coating solution also contains coarse particles of the charge generating material, Image characteristics are degraded. Therefore, in the process of preparing the charge generation layer coating solution, it is important to sufficiently disperse the charge generation material so that the coating solution does not contain secondary agglomerated particles or coarse particles.

  On the other hand, when the dispersibility of the charge generation material is increased by a high dispersion share, a uniformly dispersed coating film can be formed, but the crystal structure of the charge generation material is changed by the dispersion share and its characteristics are impaired, and sensitivity and potential stability are stabilized. May cause problems with sex.

  The present inventors have wondered whether the 2,3-butanediol adduct titanyl phthalocyanine pigment of the present invention has a high fracture surface activity when pulverized and is unstable. In other words, butanediol desorption or phthalocyanine ring decomposition due to hydrolysis or the like is likely to occur at crystal defects that occur on the fracture surface, etc. that occur when pulverized, and the decomposition products inhibit charge generation or become charge traps. Inferred that it may adversely affect sensitivity and repeatability.

  In accordance with this reasoning, the present invention has attempted to increase dispersibility without putting too much stress on the pigment crystal. As a result, it was found that the problem could be solved by synthesizing small particle size pigment particles and carrying out low shear dispersion by only loosening secondary agglomeration without crushing while maintaining the crystals at the time of pigment synthesis. As an index of low shear dispersion only, when the D50 particle diameter and D10 particle diameter of the pigment are in the following ranges, an electrophotographic photoreceptor having high sensitivity and high repeated potential stability is obtained without sensitivity dependency on humidity. It turns out that we can do it.

  That is, according to the examination results of the present inventors, at least any of titanyl phthalocyanine and (2R, 3R) -2,3-butanediol adduct or titanyl phthalocyanine and (2S, 3S) -2,3-butanediol adduct When the pigment has a D50 particle size of 100 to 300 nm and a D10 particle size of 50 to 200 nm, the pigment can be used to disperse the sensitivity. Thus, an electrophotographic photosensitive member having high sensitivity and high repeated potential stability can be obtained.

  However, the D50 particle size and the D10 particle size follow the measurement methods and definitions described below.

  Measuring method: 500 pigment particles taken with a scanning electron microscope (SEM) photograph are randomly taken out (overlapping particles are the uppermost particles), and the major axis of each particle is measured.

  Definition of D50: D50 is the particle diameter when the particles are accumulated from the smallest particles and the accumulated amount reaches 50% (250 particles) of the total number of particles.

  Definition of D10: D10 is a particle diameter when the particles are accumulated from the smallest particles and the accumulated amount reaches 10% (50 particles) of the total number of particles.

  The D50 particle size and D10 particle size of the pigment are measured using a sample obtained by coating and drying a charge generation layer coating liquid in which a charge generation material is dispersed on a polyethylene terephthalate base.

  When the particle size of D50 is less than 100 nm, or when the particle size of D10 is less than 50 nm, this indicates that the pigment crystal was crushed due to excessive dispersion share, and 2,3-butanediol was added at the defective portion of the crystal. Degradation of body titanyl phthalocyanine is likely to occur, and as a result, sensitivity and repetitive characteristics are deteriorated.

  Further, when the particle size of D50 is larger than 300 nm, or when the particle size of D10 is larger than 200 nm, it indicates that there are secondary-aggregated particles and coarse particles with poor dispersion, resulting in image defects such as fogging. It will be.

  The pigment particles according to the present invention preferably have a circularity in the range of 0.8 to 0.9. The lightness within this range can remarkably bring out the effects of the present invention.

  Here, the circularity of the pigment particles is calculated using the electron microscope image of the SEM in which D50 and D10 are calculated.

  That is, the circularity of 500 randomly selected pigment particles taken with a scanning electron microscope (SEM) photograph was measured, and the number average value was defined as the circularity.

  The circularity of the pigment here is based on the following definition.

Circularity = circumference of circle having the same projected area as pigment particles / perimeter of pigment particles The 2,3-butanediol adduct titanyl phthalocyanine pigment of the present invention is synthesized as shown in the following chemical reaction.

[Method for producing 2,3-butanediol adduct titanyl phthalocyanine pigment]
The pigment containing at least one of titanyl phthalocyanine and (2R, 3R) -2,3-butanediol adduct or titanyl phthalocyanine and (2S, 3S) -2,3-butanediol adduct of the present invention is titanyl phthalocyanine. And (2R, 3R) -2,3-butanediol or (2S, 3S) -2,3-butanediol (hereinafter sometimes referred to as butanediol compounds) in various solvents at room temperature or under heating. Can be synthesized. The raw material titanyl phthalocyanine can be synthesized from phthalonitrile and titanium tetrachloride, synthesized from diiminoisoindoline and alkoxy titanium, or synthesized from phthalonitrile, urea and alkoxy titanium. The method can also be used, but high purity titanyl phthalocyanine with a low chlorine content obtained from diiminoisoindoline and alkoxytitanium is particularly preferred. The titanyl phthalocyanine is preferably made amorphous by a method such as acid paste treatment and then reacted with a butanediol compound. For the addition reaction between amorphous titanyl phthalocyanine and a butanediol compound, usually 5 to 30 times the solvent is used. The solvent is not particularly limited, and aromatic solvents such as chlorobenzene, dichlorobenzene, anisole, chloronaphthalene and quinoline to ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and acetophenone, ether solvents such as tetrahydrofuran, dioxolane and diglyme, Furthermore, there can be mentioned a large number of aprotic polar solvents such as dimethylformamide, dimethylacetamide and dimethylsulfoxide, other halogen-based solvents and ester-based solvents.

  The reaction between titanyl phthalocyanine and a butanediol compound is shown below, but it can be carried out under a wide range of temperature conditions, and the reaction temperature is preferably in the range of 25 to 300 ° C, more preferably in the range of 30 to 100 ° C. .

  The butanediol compound is usually added at a ratio of 0.2 to 2.0 mol with respect to 1 mol of titanyl phthalocyanine. In order to be an equimolar adduct, the diol compound must be used in an amount of 1.0 mol or more. When the diol compound is added in an amount of 1.0 mol or less in the above ratio, the obtained adduct becomes a mixed crystal with titanyl phthalocyanine. As long as the particle size distribution of the present invention is satisfied, mixed crystals (mixed crystals are not mere mixtures but have a specific crystal structure) are also within the scope of the present invention.

  Furthermore, it is preferable to treat the reaction product of titanyl phthalocyanine and a butanediol compound in a solvent in the presence of water. By performing the water treatment, a mixed crystal pigment containing the 2,3-butanediol adduct titanyl phthalocyanine having a thermally stable diol addition ratio can be stably obtained.

[Crystal form of 2,3-butanediol adduct titanyl phthalocyanine pigment]
The 2,3-butanediol adduct titanyl phthalocyanine pigment of the present invention has two crystal forms depending on the difference in butanediol addition ratio.

  When an excess of titanyl phthalocyanine and at least one of (2R, 3R) -2,3-butanediol or (2S, 3S) -2,3-butanediol (hereinafter also referred to as butanediol) is reacted, In the diffraction spectrum, a pigment having a characteristic peak at a Bragg angle 2θ (± 0.2 °): 9.5 ° (hereinafter abbreviated as 9.5 ° type) is obtained as shown in FIG. The 9.5 type butanediol-added titanyl phthalocyanine raw pigment has peaks at 16.4 °, 19.1 °, 24.7 °, and 26.5 ° in addition to 9.5.

Structure of the pigment Ti = O absorption near 970 cm ^-1 in the IR spectrum disappeared, 630 cm ^-1 of the absorption of the O-Ti-O appears in the vicinity about the 390 to 410 ° C. in a thermal analysis (TG) 11 % Mass loss (possibly due to the elimination of butylene oxide by thermal decomposition), and from the results of mass spectrometry, titanyl phthalocyanine and (2R, 3R) -2,3-butanediol or (2S, 3S ) -2,3-butanediol is considered to have a dehydrated condensation structure at 1/1.

On the other hand, when a butanediol compound is reacted at 1 mol or less with respect to 1 mol of titanyl phthalocyanine, the powder X-ray diffraction spectrum has a characteristic peak at a Bragg angle 2θ: 8.3 ° (± 0.2 °) ( Hereinafter, the pigment shown in FIG. 1 (2) is obtained. The 8.3 ° butanediol-added titanyl phthalocyanine pigment has peaks at 24.7 °, 25.1 °, and 26.5 ° in addition to 8.3 °. The pigment shows both absorption of Ti = O near 970 cm ⁻¹ and O—Ti—O near 630 cm ⁻¹ in the IR spectrum. In addition, from the result of mass analysis that the mass loss is less than 11% at 390 to 410 ° C. by thermal analysis and from the result of mass analysis, butanediol / titanyl phthalocyanine = 1/1 adduct and titanyl phthalocyanine are mixed at a certain ratio ( It is simply assumed that two or more compounds are mixed in one pigment particle. The butanediol addition ratio is estimated to be 40 to 70 mol% from the mass loss of 390 to 410 ° C. in the thermal analysis.

  In the X-ray diffraction spectrum, the characteristic peak means a clearly different peak exceeding the background variation.

  In the present invention, the pigment has a characteristic peak at least at a Bragg angle (2θ ± 0.2 °) of 8.3 ° in the X-ray diffraction spectrum in that good sensitivity and repeated potential stability can be obtained. More preferably.

  In the present invention, the 2,3-butanediol adduct titanyl phthalocyanine pigment having the crystal form as described above is dispersed in a low share, that is, the stress is small, and the pigment is dispersed in a relatively short dispersion time. By dispersing the D50 particle size and D10 particle size of the pigment so as to be within the range of the present invention, a photoreceptor having the effects of the present invention, that is, good sensitivity and repeated potential stability can be produced. .

[Dispersion of 2,3-butanediol adduct titanyl phthalocyanine pigment]
In order to make a dispersion liquid such as a charge generation layer using the butanediol adduct titanyl phthalocyanine pigment of the present invention, these pigments are dispersed in a solvent. There are no particular restrictions on the solvent, and ketone solvents such as methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, cyclohexanone, and acetophenone, ether solvents such as tetrahydrofuran, dioxolane, and diglyme, and alcohol solvents such as methyl cellosolve, ethyl cellosolve, and butanol There may be mentioned a large number of solvents, ester solvents such as ethyl acetate and t-butyl acetate, aromatic solvents such as toluene and chlorobenzene, and halogen solvents such as dichloroethane and trichloroethane.

  A binder can be added to the dispersion. The binder can be selected widely as long as it is soluble in the solvent used. Examples include polyvinyl butyral, polyvinyl formal, polyvinyl acetate, polyvinyl chloride, polyamide, polycarbonate, polyester, and copolymers thereof. The ratio of the binder and the pigment is not particularly limited, but is usually 1/10 to 10/1. When the amount of the binder is small, the dispersion becomes unstable, and when the amount is too large, the electric resistance is increased, and when the electrophotographic photosensitive member is formed, the residual potential tends to increase repeatedly.

  The dispersion means preferably used in the present invention is the above-described low shear dispersion. As the low shear dispersion, a medium using ultrasonic dispersion or a medium having a small specific gravity (such as glass (specific gravity: 2.5) beads) is used. Dispersion is preferred.

[Production of photoconductor]
In preparing the organic photoreceptor of the present invention, a known technique can be used as it is. Hereinafter, the constitution of the organic photoreceptor used in the present invention will be described.

  In the present invention, the organic photoconductor means an electrophotographic photoconductor constituted by providing an organic compound with at least one of a charge generation function and a charge transport function essential to the configuration of the electrophotographic photoconductor. All known organic electrophotographic photoreceptors such as a photoreceptor composed of the above organic charge generating substance or organic charge transporting substance, a photoreceptor composed of a polymer complex with a charge generating function and a charge transporting function are contained.

  The layer structure of the organophotoreceptor is not particularly limited, but is basically a charge generation layer, a charge transport layer, or a charge generation / charge transport layer (a layer having both charge generation and charge transport functions), etc. The photosensitive layer may be a surface layer coated thereon. The surface layer preferably has a protective layer function and a charge transport function.

  Hereinafter, a specific configuration of the photoreceptor used in the present invention will be described.

(Conductive support)
As the conductive support used in the photoreceptor of the present invention, a sheet-like or cylindrical conductive support is used.

  The cylindrical conductive support of the present invention means a cylindrical support necessary for forming an endless image by rotating, and the straightness is in the range of 0.1 mm or less and the deflection is 0.1 mm or less. Certain conductive supports are preferred. Exceeding the range of straightness and shake makes it difficult to form a good image.

As a material for the conductive support, a metal drum such as aluminum or nickel, a plastic drum deposited with aluminum, tin oxide, indium oxide, or the like, or a paper / plastic drum coated with a conductive substance can be used. The conductive support preferably has a specific resistance of 10 ³ Ω · cm or less at room temperature.

  As the conductive support used in the present invention, one having an alumite film that has been sealed on the surface thereof may be used. The alumite treatment is usually performed in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, phosphoric acid, boric acid, sulfamic acid, etc., but anodizing treatment in sulfuric acid gives the most preferable result. In the case of anodizing in sulfuric acid, the sulfuric acid concentration is preferably 100 to 200 g / l, the aluminum ion concentration is 1 to 10 g / l, the liquid temperature is about 20 ° C., and the applied voltage is preferably about 20 V. It is not limited. The average film thickness of the anodized film is usually 20 μm or less, particularly preferably 10 μm or less.

(Middle layer)
In the present invention, an intermediate layer having a barrier function is preferably provided between the conductive support and the photosensitive layer, and in particular, an intermediate layer in which titanium oxide fine particles are dispersed and contained in a binder resin such as polyamide is preferable. The average particle diameter of the titanium oxide particles is preferably in the range of 10 nm to 400 nm in terms of number average primary particle diameter, and is preferably 15 nm to 200 nm. If it is less than 10 nm, the effect of preventing the occurrence of moire by the intermediate layer is small. On the other hand, if it is larger than 400 nm, the titanium oxide particles in the intermediate layer coating solution are likely to settle, and as a result, the uniform dispersibility of the titanium oxide particles in the intermediate layer is poor, and the black spots are likely to increase. An intermediate layer coating liquid using titanium oxide particles having a number average primary particle size in the above range has good dispersion stability, and the intermediate layer formed from such a coating liquid has an environmental characteristic in addition to the function of preventing the occurrence of black spots. Is good and has cracking resistance.

  The shape of the titanium oxide particles used in the present invention includes a dendritic shape, a needle shape, a granular shape, and the like. The titanium oxide particles having such a shape are, for example, titanium oxide particles, anatase type, rutile as crystal types. There are types, amorphous types, and the like. Any crystal type may be used, or two or more crystal types may be mixed and used. Among them, the rutile type and granular type are the best.

  The titanium oxide particles of the present invention are preferably surface-treated. Among these, it is preferable to perform a plurality of surface treatments, and among the plurality of surface treatments, the last surface treatment is a surface treatment using a reactive organosilicon compound. In addition, at least one of the surface treatments is at least one surface treatment selected from alumina, silica, and zirconia, and finally a surface treatment using a reactive organosilicon compound. It is preferable to carry out.

  Alumina treatment, silica treatment and zirconia treatment are treatments for precipitating alumina, silica or zirconia on the surface of the titanium oxide particles. The alumina, silica and zirconia deposited on these surfaces are water of alumina, silica and zirconia. Japanese products are also included. The surface treatment of the reactive organosilicon compound means using a reactive organosilicon compound in the treatment liquid.

  In this way, when the surface treatment of the titanium oxide particles is performed at least twice, the surface of the titanium oxide particles is uniformly coated (treated), and when the surface-treated titanium oxide particles are used for the intermediate layer, the intermediate layer It is possible to obtain a good photoconductor having good dispersibility of the titanium oxide particles therein and causing no image defects such as black spots.

  Preferable reactive organosilicon compounds used for the surface treatment include various alkoxysilanes such as methyltrimethoxysilane, n-butyltrimethoxysilane, n-hexycyltrimethoxysilane, dimethyldimethoxysilane, and methylhydrogenpolysiloxane.

(Photosensitive layer)
The photosensitive layer configuration of the photoreceptor of the present invention may be a single layer photosensitive layer configuration in which a charge generation function and a charge transport function are provided on one layer on the intermediate layer. It is preferable that the generation layer (CGL) and the charge transport layer (CTL) be separated. By adopting a configuration in which the functions are separated, an increase in the residual potential due to repeated use can be controlled to be small, and other electrophotographic characteristics can be easily controlled according to the purpose. In the negatively charged photoconductor, it is preferable that a charge generation layer (CGL) is formed on the intermediate layer, and a charge transport layer (CTL) is formed thereon. In the positively charged photoconductor, the order of the layer configuration is the reverse of that in the negatively charged photoconductor. The most preferred photosensitive layer structure of the present invention is a negatively charged photoreceptor structure having the function separation structure.

  The structure of the photosensitive layer of the function-separated negatively charged photoreceptor will be described below.

(Charge generation layer)
The charge generation layer contains a charge generation material (CGM). Other substances may contain a binder resin and other additives as necessary.

  In the organophotoreceptor of the present invention, the above-mentioned butanediol adduct titanyl phthalocyanine pigment is used as the charge generating material, but other phthalocyanine pigments, azo pigments, perylene pigments, azulium pigments and the like can be used in combination.

  When a binder is used as the CGM dispersion medium in the charge generation layer, a known resin can be used as the binder, but the most preferred resins include formal resin, butyral resin, silicone resin, silicone-modified butyral resin, phenoxy resin, and the like. Can be mentioned. The ratio of the binder resin to the charge generating material is preferably 20 to 600 parts by mass with respect to 100 parts by mass of the binder resin. By using these resins, the increase in residual potential associated with repeated use can be minimized. The thickness of the charge generation layer is preferably 0.1 μm to 2 μm.

(Charge transport layer)
The charge transport layer contains a charge transport material (CTM) and a binder resin that disperses and forms a CTM. Other substances may contain additives such as antioxidants as necessary.

  A known charge transport material (CTM) can be used as the charge transport material (CTM). For example, a triphenylamine derivative, a hydrazone compound, a styryl compound, a benzidine compound, a butadiene compound, or the like can be used. These charge transport materials are usually dissolved in a suitable binder resin to form a layer.

  The binder resin used for the charge transport layer (CTL) may be either a thermoplastic resin or a thermosetting resin. For example, polystyrene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, melamine resin, and these resins A copolymer resin containing two or more of the repeating unit structures. In addition to these insulating resins, high molecular organic semiconductors such as poly-N-vinylcarbazole can be used. Of these, polycarbonate resins are most preferred because of their low water absorption and good CTM dispersibility and electrophotographic characteristics.

  The ratio of the binder resin to the charge transport material is preferably 10 to 200 parts by mass with respect to 100 parts by mass of the binder resin. The thickness of the charge transport layer is preferably 10 to 40 μm.

  The most preferable layer structure of the photoconductor of the present invention has been exemplified above, but other photoconductor layer configurations may be used in the present invention.

  Examples of the solvent or dispersion medium used for forming the photosensitive layer include n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N, N-dimethylformamide, acetone, methyl ethyl ketone, methyl isopropyl ketone, cyclohexanone, Benzene, toluene, xylene, chloroform, dichloromethane, 1,2-dichloroethane, 1,2-dichloropropane, 1,1,2-trichloroethane, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethane, tetrahydrofuran, dioxolane, dioxane, Examples include methanol, ethanol, butanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, and methyl cellosolve. The present invention is not limited to these, but toluene, tetrahydrofuran, dioxolane and the like are preferably used. These solvents may be used alone or as a mixed solvent of two or more.

  Next, as a coating processing method for manufacturing the organic photoreceptor, a coating processing method such as dip coating, spray coating, circular amount regulation type coating, etc. is used. In order to prevent dissolution as much as possible, and in order to achieve uniform coating processing, it is preferable to use a coating processing method such as spray coating or circular amount regulation type (circular slide hopper type is a typical example). It is most preferable to use the circular amount regulation type coating method for the protective layer. The circular amount regulation type coating is described in detail in, for example, Japanese Patent Application Laid-Open No. 58-189061.

[Image forming apparatus]
FIG. 2 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of the present invention.

  In the image forming apparatus of the present invention, it is desirable to use a semiconductor laser or light emitting diode having an oscillation wavelength of 350 to 850 nm as an image exposure light source when an electrostatic latent image is formed on a photoreceptor. By using these image exposure light sources, the exposure dot diameter in the writing principal direction is narrowed down to 10 to 100 μm, and digital exposure is performed on the organic photoreceptor, so that 400 dpi (dpi: number of dots per 2.54 cm) to 2400 dpi. Or higher-resolution electrophotographic images can be obtained.

The exposure dot diameter refers to the length of the exposure beam along the main scanning direction (Ld: measured at the maximum length) in a region where the intensity of the exposure beam is 1 / e ² or more of the peak intensity.

The light beams used have a scanning optical system and LED solid scanner such as a semiconductor laser, there is a Gaussian distribution and Lorentz distribution, etc. also the light intensity distribution is in each 1 / e ² or more regions of peak intensity The exposure dot diameter according to the present invention is used.

  This color image forming apparatus is called a tandem type color image forming apparatus, and includes four sets of image forming units (image forming units) 10Y, 10M, 10C, and 10Bk, an endless belt-shaped intermediate transfer body unit 7, and a feeding unit. It comprises a paper conveying means 21 and a fixing means 24. A document image reading device SC is disposed on the upper part of the main body A of the image forming apparatus.

  The image forming unit 10Y that forms a yellow image includes a charging unit (charging step) 2Y, an exposure unit (exposure step) 3Y, and a developing unit disposed around a drum-shaped photoconductor 1Y as a first image carrier. A unit (developing step) 4Y, a primary transfer roller 5Y as a primary transfer unit (primary transfer step), and a cleaning unit 6Y. An image forming unit 10M that forms a magenta image includes a drum-shaped photosensitive member 1M as a first image carrier, a charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roller 5M as a primary transfer unit, It has a cleaning means 6M. An image forming unit 10C for forming a cyan image includes a drum-shaped photoreceptor 1C as a first image carrier, a charging unit 2C, an exposure unit 3C, a developing unit 4C, and a primary transfer roller 5C as a primary transfer unit. It has cleaning means 6C. The image forming unit 10Bk that forms a black image includes a drum-shaped photoreceptor 1Bk as a first image carrier, a charging unit 2Bk, an exposure unit 3Bk, a developing unit 4Bk, a primary transfer roller 5Bk as a primary transfer unit, and a cleaning unit. 6Bk.

  The four sets of image forming units 10Y, 10M, 10C, and 10Bk include charging means 2Y, 2M, 2C, and 2Bk that rotate around the photosensitive drums 1Y, 1M, 1C, and 1Bk, and image exposure means 3Y, 3M, 3C and 3Bk, rotating developing means 4Y, 4M, 4C and 4Bk, and cleaning means 6Y, 6M, 6C and 6Bk for cleaning the photosensitive drums 1Y, 1M, 1C and 1Bk.

  The image forming units 10Y, 10M, 10C, and 10Bk have the same configuration except that the colors of toner images formed on the photoreceptors 1Y, 1M, 1C, and 1Bk are different, and the image forming unit 10Y is taken as an example in detail. explain.

  The image forming unit 10Y has a charging unit 2Y (hereinafter simply referred to as a charging unit 2Y or a charger 2Y), an exposure unit 3Y, a developing unit 4Y, and a cleaning unit 6Y (around a photosensitive drum 1Y as an image forming body). Hereinafter, the cleaning unit 6Y or the cleaning blade 6Y) is simply disposed, and a yellow (Y) toner image is formed on the photosensitive drum 1Y. In the present embodiment, in the image forming unit 10Y, at least the photosensitive drum 1Y, the charging unit 2Y, the developing unit 4Y, and the cleaning unit 6Y are provided so as to be integrated.

  The charging unit 2Y is a unit that applies a uniform potential to the photosensitive drum 1Y. In the present embodiment, a corona discharge type charger 2Y is used for the photosensitive drum 1Y.

  The image exposure means 3Y performs exposure based on the image signal (yellow) on the photosensitive drum 1Y given a uniform potential by the charger 2Y, and forms an electrostatic latent image corresponding to the yellow image. As the exposure unit 3Y, a unit composed of LEDs and light-emitting elements in which light emitting elements are arranged in an array in the axial direction of the photosensitive drum 1Y, a laser optical system, or the like is used.

  The image forming apparatus of the present invention is configured by integrally combining the above-described photosensitive member and components such as a developing device and a cleaning device as a process cartridge (image forming unit), and this image forming unit is connected to the apparatus main body. It may be configured to be detachable. In addition, at least one of a charging device, an image exposure device, a developing device, a transfer or separation device, and a cleaning device is integrally supported together with a photosensitive member to form a process cartridge (image forming unit), which is detachable from the apparatus main body. A single image forming unit may be detachable using guide means such as a rail of the apparatus main body.

  The endless belt-like intermediate transfer body unit 7 includes an endless belt-like intermediate transfer body 70 as a second image carrier having a semiconductive endless belt shape that is wound around a plurality of rollers and is rotatably supported.

  Each color image formed by the image forming units 10Y, 10M, 10C, and 10Bk is sequentially transferred onto a rotating endless belt-shaped intermediate transfer body 70 by primary transfer rollers 5Y, 5M, 5C, and 5Bk as primary transfer means. Thus, a synthesized color image is formed. An image support P as an image support (support for supporting a fixed final image: for example, plain paper, transparent sheet, etc.) housed in the paper feed cassette 20 is fed by a paper feed means 21 and is supplied to a plurality of image supports P. The intermediate rollers 22A, 22B, 22C, 22D, and the registration roller 23 are conveyed to a secondary transfer roller 5b as a secondary transfer unit, and are secondarily transferred onto the image support P to collectively transfer color images. . The image support P to which the color image has been transferred is subjected to fixing processing by the fixing means 24, is sandwiched between the paper discharge rollers 25, and is placed on a paper discharge tray 26 outside the apparatus. Here, a toner image transfer support formed on a photosensitive member such as an intermediate transfer member or an image support is generally referred to as a transfer medium.

  On the other hand, the endless belt-shaped intermediate transfer body 70 obtained by transferring the color image to the image support P by the secondary transfer roller 5b as the secondary transfer means and then separating the curvature of the image support P is subjected to residual toner by the cleaning means 6b. Removed.

  During the image forming process, the primary transfer roller 5Bk is always in contact with the photoreceptor 1Bk. The other primary transfer rollers 5Y, 5M, and 5C are in contact with the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.

  The secondary transfer roller 5b contacts the endless belt-shaped intermediate transfer body 70 only when the image support P passes through the secondary transfer roller 5b and the secondary transfer is performed.

  Further, the housing 8 can be pulled out from the apparatus main body A through the support rails 82L and 82R.

  The housing 8 includes image forming units 10Y, 10M, 10C, and 10Bk and an endless belt-shaped intermediate transfer body unit 7.

  The image forming units 10Y, 10M, 10C, and 10Bk are arranged in tandem in the vertical direction. An endless belt-shaped intermediate transfer body unit 7 is disposed on the left side of the photoreceptors 1Y, 1M, 1C, and 1Bk in the drawing. The endless belt-shaped intermediate transfer body unit 7 includes an endless belt-shaped intermediate transfer body 70 that can be rotated by winding rollers 71, 72, 73, 74, primary transfer rollers 5Y, 5M, 5C, 5Bk, and cleaning means 6b. Consists of.

  The image forming apparatus of the present invention is generally applicable to electrophotographic apparatuses such as electrophotographic copying machines, laser printers, LED printers, and liquid crystal shutter printers. The present invention can be widely applied to such devices.

  In the following, the configuration and effects of the present invention are shown in the embodiments, but of course, the embodiments of the present invention are not limited to these. In addition, “part” in the sentence represents “part by mass”.

Synthesis example 1
(Synthesis of amorphous titanyl phthalocyanine)
1,3-diiminoisoindoline; 29.2 g was dispersed in 200 ml of orthodichlorobenzene, titanium tetra-n-butoxide; 20.4 g was added, and the mixture was heated at 150 to 160 ° C. for 5 hours in a nitrogen atmosphere. After allowing to cool, the precipitated crystals were filtered, washed with chloroform, washed with 2% aqueous hydrochloric acid, washed with water, washed with methanol, and dried to obtain 26.2 g (yield 91%) of crude titanyl phthalocyanine. Next, the crude titanyl phthalocyanine was dissolved by stirring in 250 ml of concentrated sulfuric acid at 5 ° C. or lower for 1 hour, and this was poured into 5 L of water at 20 ° C. The precipitated crystals were filtered and sufficiently washed with water to obtain 225 g of a wet paste product. The wet paste product was then frozen in a freezer, thawed again, filtered and dried to obtain 24.8 g of amorphous titanyl phthalocyanine (yield 86%).

(Synthesis of (2R, 3R) -2,3-butanediol adduct titanyl phthalocyanine CG-1)
The above-mentioned amorphous titanyl phthalocyanine (10.0 g) and (2R, 3R) -2,3-butanediol (1.30 g) (0.83 equivalent ratio) (equivalent ratio is equivalent ratio to titanyl phthalocyanine, hereinafter the same) were combined with orthochlorobenzene (ODB). ) The mixture was mixed in 200 ml and stirred at 60 to 70 ° C. for 6.0 hours. After standing overnight, 100 ml of water was added to the reaction solution, and the mixture was heated and stirred at 60 to 70 ° C. for 6.0 hours to conduct a hydrolysis reaction (hydrolysis step). After the hydrolysis reaction, the reaction solution is allowed to cool, and the resulting crystals are filtered by adding methanol. The filtered crystals are washed with methanol ((2R, 3R) -2,3-butanediol adduct titanyl phthalocyanine). Pigment containing CG-1: 10.3 g was obtained. The X-ray diffraction spectrum of CG-1 has clear peaks at 8.3 °, 24.7 °, 25.1 °, and 26.5 ° as shown in (2) of FIG. There is a peak in the 576 and 648 in the mass spectra, O-Ti-O both absorption appears Ti = O near 970 cm ^-1, around 630 cm ^-1 in the IR spectrum. In addition, since thermal analysis (TG) has a mass loss of about 7% at 390 to 410 ° C., a 1: 1 adduct of titanyl phthalocyanine and (2R, 3R) -2,3-butanediol (shown in Chemical Formula 1 above) A dehydrated condensation structure) and a non-adduct (not added) titanyl phthalocyanine mixed crystal.

Synthesis example 2
(Synthesis of (2S, 3S) -2,3-butanediol adduct titanyl phthalocyanine CG-2)
(2S, 3S) -2,3 in the same manner as in Synthesis Example 1 except that (2S, 3S) -2,3-butanediol was used instead of (2R, 3R) -2,3-butanediol. -Pigment CG-2 containing butanediol-titanyl phthalocyanine adduct was obtained: 10.5 g. In the X-ray diffraction spectrum of CG-2, clear peaks are observed at 8.3 °, 24.7 °, 25.1 °, and 26.5 °.

Synthesis example 3
In the reaction of amorphous titanyl phthalocyanine of Synthesis Example 1 and (2R, 3R) -2,3-butanediol, the reaction temperature was changed to 100 to 110 ° C. instead of 60 to 70 ° C. (2R , 3R) -2,3-butanediol adduct, pigment CG-3 containing titanyl phthalocyanine: 10.6 g was obtained. In the X-ray diffraction spectrum of CG-3, clear peaks are observed at 8.3 °, 24.7 °, 25.1 °, and 26.5 °.

Production of Photoreceptor 1 An intermediate layer coating solution having the following composition was dip coated on a cylindrical aluminum substrate to form an intermediate layer having a thickness of 4.0 μm.

<Intermediate layer coating solution>
The following composition was dispersed using a circulating wet disperser.

Polyamide resin “CM8000” (manufactured by Toray Industries, Inc.) 10 parts Titanium oxide (number average primary particle size 35 nm, primary surface treatment; silica / alumina treatment, secondary surface treatment; methyl hydrogen polysiloxane treatment) 30 parts Methanol 100 parts Above The following charge generation layer coating solution was applied by dip coating to form a charge generation layer having a thickness of 0.3 μm.

<Charge generation layer coating solution>
The following composition was mixed and dispersed for 1 hour in a circulating ultrasonic homogenizer RUS-600TCNP (manufactured by Nippon Seiki Seisakusho Co., Ltd.) (circulating US dispersion 1 hour).

Charge generation material: CG-1 of Synthesis Example 1 24 parts Polyvinyl butyral resin “ESREC BL-1” (manufactured by Sekisui Chemical Co., Ltd.) 12 parts 2-butanone / cyclohexanone = 4/1 (V / V) 400 parts A charge transport layer coating solution mixed with the above composition was applied and dried by heating at 110 ° C. for 60 minutes to form a charge transport layer having a film thickness of 20 μm.

<Charge transport layer coating solution>
Charge transport material: (4-methoxy-4 ′-(β-phenyl-4-methylstyryl) triphenylamine) 200 parts Polycarbonate “Iupilon Z300” (manufactured by Mitsubishi Gas Chemical Company) 300 parts 2,6-di-t- Butyl-4-phenylphenol 5 parts Toluene / tetrahydrofuran = 1/9 (v / v) 2000 parts The above charge generation layer was dried on a transparent pet base, coated and dried at a film thickness of 0.3 μm, D50 particle size, A sample for measuring D10 particle size and circularity was used.

  However, the D50 particle diameter, D10 particle diameter, and circularity follow the measurement method and definition described above.

  The results obtained are shown in Table 1.

Production of Photoreceptor 2 Photoreceptor 2 was produced in the same manner as in Photoreceptor 1 except that the dispersion time of the charge generation material coating solution was changed to 3 hours.

Production of Photoreceptor 3 Photoreceptor 3 was produced in the same manner as in Photoreceptor 1 except that CG-2 obtained in Synthesis Example 2 was used as the charge generation material.

Production of Photoreceptor 4 Photoreceptor 4 was produced in the same manner as in Photoreceptor 1 except that the charge generation layer coating solution was changed to ultrasonic dispersion under the following conditions (batch type US dispersion 2 hours).

<Charge generation layer coating solution>
The following compositions were mixed and subjected to ultrasonic dispersion for 2 hours in an ultrasonic cleaning tank of 28 kHz and 500 W.

Charge generation material: CG-1 of Synthesis Example 1 24 parts Polyvinyl butyral resin “ESREC BL-1” (manufactured by Sekisui Chemical Co., Ltd.) 12 parts 2-butanone / cyclohexanone = 4/1 (V / V) 400 parts Production Photoconductor 5 was produced in the same manner as in photoconductor 4, except that the dispersion time of the charge generation material coating solution was changed to 5 hours.

Production of Photoreceptor 6 Photoreceptor 6 was produced in the same manner as in Photoreceptor 1 except that the charge generation layer coating solution was changed to sand mill dispersion under the following conditions (glass beads dispersion 1 hour (rotation speed 1000 rpm)).

<Charge generation layer coating solution>
The following composition was mixed, and glass (specific gravity: 2.5) beads having an outer diameter of 1 mm were used as dispersion media, and dispersion was performed for 1 hour in a sand mill under conditions of a bead filling rate of 80% by volume and a rotation speed of 1000 rpm.

Charge generation material: CG-1 of Synthesis Example 1 24 parts Polyvinyl butyral resin “ESREC BL-1” (manufactured by Sekisui Chemical Co., Ltd.) 12 parts 2-butanone / cyclohexanone = 4/1 (V / V) 400 parts Production Photoconductor 7 was produced in the same manner as photoconductor 1 except that CG-3 obtained in Synthesis Example 3 was used as the charge generation material.

Production of Photoreceptor 8 In the same manner as in Photoreceptor 6, except that CG-3 obtained in Synthesis Example 3 was used as the charge generation material and the dispersion time of the charge generation layer coating solution was changed to 3 hours. Produced.

Production of Photoreceptor 9 Photoreceptor 9 was produced in the same manner as in Photoreceptor 6, except that the rotation speed of the charge generation layer coating solution was changed to 1500 rpm.

Production of Photoreceptor 10 Photoreceptor 10 was produced in the same manner as in Photoreceptor 6, except that the glass beads in the charge generation layer coating solution dispersion conditions were changed to zirconia (specific gravity: 6.0) beads.

  For the photoconductors 2 to 10, the D50 particle size, D10 particle size, and circularity were measured in the same manner as the photoconductor 1. The results are shown in Table 1.

  Photoconductors 1 to 10 produced as described above were incorporated into a digital copying machine bizhub 920 (manufactured by Konica Minolta Business Technologies), and an image output test was performed.

Characteristic evaluation Characteristic evaluation was performed according to the following criteria.

<Humidity memory>
The digital copying machine bizhub 920 was left in a high temperature and high humidity environment (HH: 33 ° C., 80 RH%) for 24 hours, then placed in a low temperature and low humidity environment (LL: 10 ° C., 20 RH%), and copied after 30 minutes. A halftone image having a density of 0.4 in the original image was copied to a density of 0.4, and a determination was made based on the density difference (ΔHD = maximum density−minimum density) of the copy image. The image density was measured using a Macbeth RD-918.

A: ΔHD is 0.05 or less (good)
○: ΔHD is larger than 0.05 and smaller than 0.1 (no practical problem)
X: ΔHD is 0.1 or more (practical problem)
<Evaluation of initial and post-endurance images>
An actual image test was conducted 200,000 times in a high-temperature and high-humidity environment (HH), and image evaluation was performed.

  Each evaluation item and criteria are as shown below.

Image density:
A solid black image was produced on white A4 paper, and the image density was measured using RD-918 manufactured by Macbeth. The relative reflection density was measured with the paper reflection density set to “0”. As the residual potential increases on multiple copies, the image density decreases.

A: Black solid image is 1.2 or more B: Black solid image is less than 1.0 to less than 1.2 X: Black solid image is less than 1.0 Image fog:
Using a Macbeth reflection densitometer “RD-918”, the density of unprinted copy paper (white paper) is measured at 20 locations in absolute image density, and the average value is defined as the white paper density. Next, the white background portion of the copy image was similarly measured at 20 locations at the absolute image density, and the value obtained by subtracting the white paper density from the average density was evaluated as the fog density. If the decrease in the charging potential is increased, fogging occurs.

A: Solid white image density is less than 0.005 (good)
○: Solid white image density of 0.005 or more and less than 0.01 (no problem in practical use)
X: 0.01 or more (practical problem)

  It can be seen that the photoreceptors 1 to 7 in the present invention have at least any practical problem, but the photoreceptors 8 to 10 outside the present invention have at least any problem.

Production of Photoreceptor 11 Photoreceptor 10 was produced in the same manner as in Photoreceptor 6, except that CG-1 of the charge generation layer was replaced with Y-type titanyl phthalocyanine (Y-type tita). Y-type titanyl phthalocyanine is a titanyl phthalocyanine pigment having a maximum peak at 27.2 ° in an X-ray diffraction spectrum (FIG. 3), and is a pigment synthesized according to the following synthesis example.

Example of synthesis of Y-type titanyl phthalocyanine A titanyl phthalocyanine crude product was synthesized from diiminoisoindoline and titanium tetrabutoxide, dissolved in sulfuric acid, poured into water, filtered, washed thoroughly with water, and containing amorphous titanyl phthalocyanine pigment in water. A paste was obtained. This pigment hydrous paste (about 10 g in terms of solid content) was dispersed in a mixture of 100 ml of orthodichlorobenzene and 100 ml of water (the water layer was separated), heated at 70 ° C. for 6 hours, and then poured into methanol to form crystals. Was filtered and dried to obtain Y-type titanyl phthalocyanine.

  The photoreceptor 11 was evaluated in the same manner as the photoreceptor 1. The results are shown in Table 3.

  As is apparent from Table 3, the photoconductor 11 using Y-type titanyl phthalocyanine as a charge generation material has good image density and fog evaluation as in the photoconductor 1 of the present invention, but the humidity memory is evaluated. Inferior.

1Y, 1M, 1C, 1Bk photoconductor 2Y, 2M, 2C, 2Bk charging unit 3Y, 3M, 3C, 3Bk exposure unit 4Y, 4M, 4C, 4Bk developing unit 10Y, 10M, 10C, 10Bk image forming unit

Claims (3)

In an organic photoreceptor having a photosensitive layer on a conductive support, the photosensitive layer comprises titanyl phthalocyanine and (2R, 3R) -2,3-butanediol adduct or titanyl phthalocyanine and (2S, 3S) -2,3- An electrophotographic photoreceptor comprising a pigment containing at least one of butanediol adducts, wherein the pigment has a D50 particle size of 100 to 300 nm and a D10 particle size of 50 to 200 nm.
However, the D50 particle size and the D10 particle size follow the measurement methods and definitions described below.
Measuring method: 500 pigment particles taken with a scanning electron microscope (SEM) photograph are randomly taken out (overlapping particles are the uppermost particles), and the major axis of each particle is measured.
Definition of D50: D50 is the particle diameter when the particles are accumulated from the smallest particles and the accumulated amount reaches 50% (250 particles) of the total number of particles.
Definition of D10: D10 is a particle diameter when the particles are accumulated from the smallest particles and the accumulated amount reaches 10% (50 particles) of the total number of particles.   The electrophotographic photosensitive member according to claim 1, wherein the pigment has a circularity of 0.8 to 0.9.   A means for forming an electrostatic latent image on the electrophotographic photosensitive member according to claim 1, a means for developing the electrostatic latent image with toner, a means for transferring the formed toner image to an image support, a transfer An image forming apparatus comprising at least means for fixing a subsequent toner image.

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